Impregnated wood and process of treating wood



Patented Oct. 6, 1925.

UNITED STATES PATENT OFFICE.

JOSEPH R. COOLIDGE, 3]), OF BROOKLINE, MASSACHUSETTS, ASSIGNOR TO IONTAN,

INQ, OF BOSTON, MASSACHUSETT$, A CORPORATIONOF MASSACHUSETTS.

ImrREeNATEpwooD AND PROCESS or 'rnm'rmawoon.

No Drawing.

To all whom it may concern:

Be it known that LJosErH R. OOOLIDGE, 3d, a citizen of the United States, residing at Brookline, in the county of Norfolk and 5 State of Massachusetts, have invented certain new and useful Improvements in Impregnated lVoods and Processes of Treating Woods, of which the following is a specification. I

This invention relates to the treatment of wood withmaterials designed to improve its characteristics. It is the general object of the invention to increase the durability of wood, to eliminate certain of its objectionable properties, and to impart to it qualities which will increase its usefulness.

While wood has always been used very extensively in a great many industries, it possesses, nevertheless, certain objectionable ceptibility to decay and its tendency, to

shrink and swell with changing moisture conditions. While these characteristics are well known and widely recognized, and wood is very generally used notwithstanding them,

still they do limit seriously the extent to which wood can be used for some purposes,

' particularly since the price of. desirable woods has become so high. This is well illustrated in the use of wooden poles by the telegraph, telephone, and electric light companies to support the wires which transmit electrical energy, Usually the more resistant woods, such as cedar and chestnut, are used for this purpose, but such poles only last on an average from eight to twelve years. The less resistant woods have an even shorter life. When these woods were very-abundant the short life of such poles was not a particularly serious factor, but today the chestnut growth suitable for poles has almost entirely disappeared from the United Statesand cedar poles are now being shipped from the Pacific Coast States to supply the eastern market. Twenty years ago chestnut poles of a standard size could be purchased freely in the eastern States for about five dollars per pole. Today such poles are very scarce and awestern cedar pole of the same dimensions commands a price of approximately twenty-five dollars in the eastern market. Furthermore, the labor expense involved in re-setting a pole has increased tremendously. C01

very important factor to the electric light.

characteristics such, for example, as its susposed to the weather. That is, the creosote purposes.

Application filed February 2, 1925. Serial No. 8,488.

quently, the short life of wooden poles is a '55 telegraph and telephone companies.

The readiness with which wood absorbs water and gives it pp, with the consequent swelling and shrinking of the wood, is also. an objectionable characteristic of this ma teral. This is true, for exaniple, in using wood in the making of atterns for castings. in lasts for the manu acture of shoes and other footwear, and in furniture where the shrinkin and swelling of the wood causes the furniture to crackand opens the joints. It is further objectionable in flooring, in wooden boats where the shrinking and swelling must be taken care of by calking, and in many other uses.

It has been proposed heretofore to overcome certain of these objections, particularly that of decay, by saturating the wood with toxic preservatives. The most satisfactory preservative for wood so far discovered is creosote, and while this is widely used on railroad ties, piles and the like, it exudes freely from the wood at atmospheric temperatures and therefore renders the Wood totally unfit for other uses where it must be handled or where it comes in contact with the person or clothing of individuals. Much of the creosote also is lost after a relatively few years when the creosoted timber is exexudes from the cells of the wood in warm weather. particularly under the action of the sun, and the creosote so exposed on the surface of the wood is washed away by rains and its efiectiveness is lost.

It has also been proposed to impregnate wood with other materials which are known tobe water resistant, such for example, as the asphalts, resins and gums, but none of these materials becomes sufliciently fluid at the-temperatures to which Wood can be sub-. jected without injuring its fibre to permit them to be introduced into the tracheids of the wood. While they might be so introduced bysolution in solvents, this procedure involves additional practical difiiculties and increases the expense of the treatment to such a degree that it is not feasible for most The present invention deals especially with the problem of preserving wood again t I decay and making-it substantially imperany tackiness or greasiness at the maximum temperature to which the wood naturally- 4 below 250 F., and I prefer to use a temperas' vious to moisture.

To accomplish this object requires the impregnation of the wood with a material hav- 1n the following characteristics:

Tirst: It must be waterproof. The fibre of the wood itself is not waterproof, but, on the contrary, has a marked afiinity for water. Consequently, in or'dento render the wood waterproof the fibre of the wood must be protected b a wate roof materiali Second: t must hard and devoid of will be subjected while in use. 'Wood exposed to the sun on summer days ma attain a temperature of 130? F. or 140 Gonsequently theimpregnating material must be able td withstand .this temperature without becoming sticky or greasy.

Third: The material must become sofluid at 250 F. or lower, that it can be introduced into the tracheids of the wood so that a thorou h impregnation of the wood can be effected. The temperature limit of 250 F. is fixed by the fact that if wood is exposed to a substantially higher temperature for any great length of time its structure is weakened. The impre nation process, there-f fore, should be carrie on at a temperature ture of about 225 F. I This r uirement also involves the question of viscosity of the mamust be of such a nature as'to prevent the growth of the fungi that produce decay.

A poise is the absolute unit of viscosity and may be defined as a force equivalent to one dyne per square centimeter. For com-. parative pur ses it may be mentioned that water at or inary temperatures has a viscosity of approximately .01 'poises, while an 88% solution of glycerine in water at ordinary temperatures has a viscosity of approx imately two poises.

It may be noted here that by the term tracheids I mean the microsco ic cells which make up the greater part of t e wood and which are known in wood structure as tracheids, fibre tracheids or libriform fibres. Also, by the term pores I mean the vessels and ducts of the wood.

I have found that montan wax not only fulfills all of these requirements and im-' parts to the wood the preservative and waterproof characteristics which are particularly desired, but that it also advanis completed tageously changes the properties of the wood in certain other res ts. A piece of wood which has been A? orou hly impr ated with montan wax and t e ores an tracheids thereof completely fille with the wax, is thereby rendered impervious to moisture, the growth of fungi in the wood is inhibited so that the wood will not decay, and furthermore, the wood so treated is an excellent electrical insulator, and it can be polished simply by cutting or abrading it to produce a smooth surface thereon.

The montan wax itself is highly water: proof so that when the res and tracheids of the wood are filled wit this wax it is impossible for water to work into the wood. This effectually eliminates any possibility of the wood shrinking or swelling. The presence of both air and moisture are required for the growth of the fungi. that produce decay, andsince the montan wax effectually seals the cells of the wood against the entrance of either air or moisture, it effectually preserves the wood.

While dry wood itself is a good insulator, it is imposisble to keep it dry under normal conditions of use because of the hy oscopic nature of wood. The montan wax, owever, excludes the water from the wood and it therefore preserves the wood in its most favorable condition foruse as an insulator.

, The ability of the impregnated wood to take a polish simply by making the surface thereof smooth, is an extremely important advantage in the manufacture of furniture and other. wooden articles which are customarily varnished or finished in some similar manner. If the impregnation process rior to the shaping of the article, the p aning, turning, sanding, or other operations required to produce such shaping also produces a finish on the article,

it simply being necessary to dust the surface of the work when it is completed, and to- I rub it somewhat if a higher polish is required. If desired, the manufacturing operations may be completed before the article i is impregnated and the surface of the finished article may then be buffed to produce the finish or polish required.

Mo'ntan wax is a native mineral wax which is usually importedbut is'readily obtainable at a moderate expense and in large quantities. The usual source of supply is lignite or pyropissite from which the inontan wax is extracted by means of solvents.

In impregnating the wood with this mate rial the montan wax is melted and it may then be forced into thefwood by either the open tank or pressure tank processes commonly used in impregnating wood with creosote oil. I prefer, however, to use the pre'ssure process, and this process may be'car- V ried out with apparatus similar to that used in creosoting railroad ties. Very minor esses of wood impregnation.

hard wood such as beech, birch and maple,

' pounds for three hours. The

modifications in such apparatus may :be

\ found desirable, such as steamjacketing the temperature preferably of from 225 to 250 F. and under a. ressure preferably of from 125 to 200 poun 's per s uare inch. The tempenature, pressure, an length of time required to effect the desired impregnation will vary somewhat with the nature of the wood, the size of the pieces, and the degree of impregnation desired, as will readily be appreciated by those familiar with the proc- In treating I have'obtained very satisfactory resultsby carrying on the impregnation at a temperature of 225 F. under a pressure 0 200 wood is then removed and allowed to cool. A considerable part of the montan wax is ejected from the wood during the process of cooling, but an ample quantity hardensin the pores and tracheids of the wood to produce the results above described.

If it is desired to recover a large art of the wax forced into the wood, this can e done by removing the ressure but maintainimg the temperature high while the Wood is allowed to drain. This will result in the pores and tracheids of the wood being partly emptied of the wax forced into them, while still leaving the cell walls thoroughly coated and the fibre of the wood effectually protected by the montan wax. When it is desired to retain a greater quantity of wax in the wood, the wood is allowed to cool down to a point near the solidification temperature, while still under pressure, before it is removed from the tank.

I find that I can produce a complete or through and through im re'gnation of the more common lrard w' s. such as beech, birch, maple and red oak. The woods which are naturally non-resistant take the treat-- ment more readily than those which are more resistant to decay. The sap wood of spruce is very readily impregnated while the heart wood takes the treatment with more difficulty. This, however, is an advantage in treating spruce for use as poles, since the impregnation of the sap wood is sufficient to protect the pole from decay, with a minimum use of impregnating material. The montan wax, however, can be made to penetrate the heart wood of spruce to a very substantial extent.

The quantity of montan wax retained in the wood can be varied and the amount of material imprisoned or sealed within the wood will be controlled in accordance with I the use to be made of the wood and consid- V erations of economy. I prefer, however, to retain in the wood at. least ten per cent of its own dry weight of montan wax. For most woods this means increasin its weight by at least two pounds per cubic foot of wood. The amount of montan wax held in the ,wood can be increased very substantially above these minimum figures, and for most purposes will be increased. In fact, I have found it possible to force into such woods as beech, birch and maple, over half of their own dry weight of montan wax. Even when a relatively small-percentage of im regn'atin'g compound is to be retained in t e wood it is preferable to force into it initially a much larger amount to secure uniform penetration, and then to allow the surplus material to dnain off after the pressure has been removed, but while the temperature is maintained relatively high. .This ensures a more uniform impregnation than could otherwise be obtained.

Preferably the wood be thoroughly dry. It is important that any excess moisture be driven off before it is attempted to force wax into the wood. There is great danger, however, in boiling off this water that the wood will crack or check. I have discovered that this difliculty can be effectually overcome by subjecting the wood to a light preliminary pressure of, say, from twenty to fifty pounds per square inch while the water is being evaporated. That is, the wood is immersed in the montan wax in the cylinder, as above to be treated should described, heat being supplied to the wax to keep it at the desired temperature, and the pressure applied is regulated between the limits above mentioned, say, for example, at forty pounds per square inch, and is maintained at this point for the time required to drive off thewater. This may be p from one to four hours. It obviously would be more economical to drive off the water at atmospheric pressure, but this would involve danger of checking the wood. By

applying a light preliminary pressure, as-

there is no danger of its checking. In fact,

when a checked piece of wood has been treated by this process it'will not check further, but it will be preserved in the condition in which it is left by the treatment. This is timber have been treated to preserve them.

Telephone poles which have been butt treated and set up out-of-doors very often check or crack open above the ground, frequently splitting to the very heart of the pole. This admits water to the interior of the pole and allows decay to start at the butt of the pole inside the area which has been treated with preservative.

The treatment with montan wax above described effectually prevents checking and it acts as a cement or binder.

preserves wood which has been checked, partly by excluding moisture from the wood, and partly, also, due to the fact that when the montan wax has hardened in the wood The .wax itself does not expand or contract appreciably with atmospheric changes, and consequently, it holds the wood in a fixed and stable condition. None of the prior treatments of which I have been able to learn has this advantage.

While, as above stated, I have found montan wax best suited to the purposes of this invention, other substances having the characteristics above defined may be substituted for it. I have discovered that carnauba wax or candelilla. wax possess some of the advantages of montan wax and that they may be used instead of montan wax in impregnating wood which is to be used for furniture and similar purposes. They both, however, are open to the objection of being far more expensive than montan wax and are, at the present time, obtainable in only limited quantities. Furthermore, carnauba wax has the characteristic-of shrinking greatly upon cooling, and when a piece of wood impregnated with carnauba wax cools, the contraction of the waxcompresses the wood so strongly that its shape is often changed.

It is also entirely possible to use other materials with montan wax to produce special effects. For example, in impregnating telephone poles, piles, posts, andother articles of wood which are to be used out-of-doors, such for example, as cross arms for telephone poles, piazza flooring, insulator pins, and the like, where the essential object is to make the wood waterproof and to preserve it, I find it not only feasible, but preferable,

to combine a substantial percentage of creosote oil with the montan wax. This wax,

unlike most others, forms a-very stable compound when mixed with creosote oil, and does not have the tendency to separate from the oil which most waxes, even including candelilla and carnauba do have, and which is extremely pronounced in the case of waxes of t e paraflin series. A mixture of montan wax and creosote oil in the proportions of sixty percent by weight of the former to forty per cent of the latter form a composition which at normal temperatures has a waxy consistency, is highly waterproof, and is a good fungicide; This mixture is sufliciently fluid at 225 F. to flow readily into the tracheids of the wood "during impregnation, the'term flow being used to esignate the movement of the liquid. 1 whether produced by' pressure, capillarity,

or otherwise. The surface of the im regnated wood will not soften or become lac yor greas solubI at temperatures below 140 F. Oil, a e coloring materials will also mix with this composition so that the wood can be colored as well as preserved. It has been definitely determined that .34 of a pound of grade 0 creosote oilper cubic foot of wood is suflicient to rotect the wood from decay. I have foun it entirely feasible toput in several pounds of creosote oil per cubic foot of wood in a mixture of the character just described. Furthermore, the toxicity of the solution maybe even further increased by using other grades of creosote, such for instance, as'that known commonly as fraction 2 creosote oil which has three times the toxic strength of grade 0. B

impregnating a pole, post, or the like, with a mixture of this character the wood is not only given a toxicity which is ample to protect it from deca but the toxic agent will be permanently held in the wood by the montan wax and prevented from exuding or oozing from the cells of the wood.

An especially important practical advantage of this feature of the present invention is that the relatively nonresistant woods, such for example, as spruce and the common southern yellow pines, can be treated by this process and thus made far superior to either chestnut or cedar for use as telephonepoles, piling, posts, cross arms, insulator pins, and mpst of the uses for which the more resistant ,woods have been used 7 almost exclusively modify the polish or finish produced by the wood for furniture and predominate in any of these mixtures.

An especially important advantage produced by this invention in the finis ing of furniture, flooring, and other wooden ar-.

ticles is that the structure of the Wood is changed either throughout, or at least for a substantial depth, as distinguished from the surface staining and finishing that is produced by the usual methods. Through the use of solvents, stains may be introduced'into 1 the wood for a very short: distance, say for b this process will successfully economical both in labor and materials than example, one-sixteenth of an inch, but no impregnation of substantial depth is produced. By my process, however, the characteristics of the woodare changed for a substantial depth or even throughout the en tire piece, dependin upon the degree to which the impregnation is carried. Consequently, a piece of furniture impregnated withstand a use that would ruin an art1cle of furniture finished by the ordinary methods.

That is, bruises, nicks, and scratches in the finished surface of a piece of furniture impregnated with a composition in which montan wax predominates, can be easily shaved or bufi'ed out, and the act of producin a smooth surface on the article also repro uces the original finish. Similar injuries to a varnished surface would require the removal of the varnishfrom the entire surface and a complete refinishing of the article. Furthermore, my-process 1s far more the usual processes.

In treatmg wood for insulation, it may be desirable to mix transil oil or some other insulating material with the wax, and I have found that compositions of this character can be used verysatisfactorily, care, of

.course, being taken to .see that any mixture the wood, they do lodge in the larger pores or vessels in the surface of the wood and thus protect it. Such a treatment is'valuable-for.

nited with some difficulty, so that the addition of asuitable fire-proofing agent makes a shingle treated by this process relatively resistant to fire.

The protection of the wood agamst fire The montan wax itself is can also be effected to advantage by introducmg a solution of one of the water soluble, fire-retarding agents, such for exam le, as ammonium chloride, into the woo'c'li and. subsequently drying the wood and then impregnating it with montan wax. The wax effectually prevents the ammonium chloride from leaching out of the wood.

A very important practical advant this invention is that it makes many, 0 the cheap and relatively plentiful woods superior for many uses to woods that are not so abundant and are considerably more-expensive. For example, it permlts the use of spruce for telephone, telegraph, and electric light poles in place of chestnut and cedar. Beech, birch and maple can be treated by this process to resemble very closely mahogany and walnut, and they are given properties which actually make them superior to mahogany and walnut in some respects.

cur to those familiar with wood and Wood products. 7

The present application is a continuation of my earlier applications Serial No. 626,818, filed March 22, 1923, and Serial No. 733,152, filed August 20, 1924, so far as the subject matter common to said applications and the present case is concerned. I

Having thus described my invention, what I desire to claim as new is:

1. An article of the character described consisting of wood impregnated fora substantial depth with a waxy material which remains hard and non-tacky at temperatures Locust is preferred at the present ,tlme for insulator pins, but a beech, birch below 130 F. but is sufiiciently fluid at 250 F. to be introduced into tracheids of thewood.

2. An article of the character described consisting of wood impregnated for a substantial depth with a waxy material which is hard and non-tacky at temperatures below 130 F.,'has a viscosity at 225,F. of between .075 and 2.00 poises and is sufiiciently fluid at 250 F. to flow into the tracheids of the wood. I

article of the character described 3. A31 'consist g of wood impregnated for a substantial depth with a toxic preservative combined with a wax material which remains hard and non-tac at temperatures below 140 F. but is sufficiently fluid at 250 F. to be introduced into the tracheids of the wood.

4. An article of the character described consisting of Wood impregnated with a toxic quantity of creosote oil combined with a proportion of a hard waxy material which prevents the oil from oozing from the surface of the wood at temperatures below 130 F., said waxy material becoming sufliciently fluid at 250 F. to flow into the tracheids of the wood.

5. An article of the character described consisting of wood carrying in the pores and tracheids thereof for a considerable depth a composition consisting chiefly of montan Wax and a toxic preservative.

6. An article of the character described consisting of wood impregnated .with a toxic quantity of creosote oil and containing asuflicient proportion of montan wax associated with said oil to prevent the oil from oozing from the surface of the wood at temperatures below 130 F.

7.. An article of the character described consisting of wood impregnated with a mixture of creosote oil and montan wax in such proportions and quantity that the wood has a toxicity equivalent to at least three-tenths of a pound of grade C creosote oil per cubic foot of wood, and the quantity of montan wax being sufiicient to prevent the creosote oil from oozing from the surface of the wood at temperatures below 130 F. ,7

8. An article of the character described consisting of wood impregnated for a substantial depth with a composition in which montan wax predominates.

9. An article of the character described consisting of wood impregnated for a substantial depth with montan wax.

10. That improvement in the process of treating wood to render it resistant to decay which consists in forcing into the pores and tracheids of the wood a melted mixture of a toxic preservative and a waxy substance which is hard and non-tacky, at temperatures below 130 F; but becomes sufficiently fluid at 250 F. to flow into the tracheids of the wood, and allowing the wood to cool sufliciently to cause the mixture to harden within the pores and tracheids.

11. That improvement in the process of treating wood which consists in forcing into the pores and tracheids of the wood a meltedwaxy material which is hard and non-tacky at temperatures below 130 F. but becomes sufficiently fluid at 250 F. to flow into the tracheids of the wood, and subsequentlv allowing the wood so treated to cool sufficiently to cause said waxy material to harden in the pores and tracheids thereof;

12. That improvement in the process of treating wood which consists in impre nating the wood for a substantial dept with a composition in which montan wax predominates.

13. That improvement in the'process of treating wood which consists in impregnating the wood for a substantial depth with montan wax. I

14. That improvement in the process of treating Wood containing excess water to impregnate it with a waxy substance which is hard at temperatures below 130 F. but becomes sufficiently fluid at 250 F to flow into'the tracheids of the wood, which consists in melting said substance, immersing the wood in the liquid so produced, driving the excess water out of the wood by heat transmitted to the wood through said liquid, maintaining a light preliminary pressure on said wood and liquid while said water is being driven o fl', and, after the desired amount of water has been driven out of the wood, increasing the pressure sufficiently to force said liquid into the pores and tracheids of the wood.

15. The process of preventing checking in wood during, the impregnation thereof with a waxy substance which is hard at temperatures below 130 F. but becomes sufiiciently fluid at 250 F. to flow into the tracheids of the wood, which consists in melting said substance, immersing the wood in the hot liquid so produced, boiling the excess water out of the wood while so immersed by heat transmitted to the wood through said liquid, maintaining a pressure of from twenty to fifty pounds on the wood and liquid during said operation of driving oil the water, and subsequently, after the excess water has been driven off, increasing the pressure on the wood and liquid sufiiciently to force said liquid into the pores and tracheids of the wood.

JOSEPH 'R. OOOLIDGE, III. 

